Hot Deformation and Processing Maps of Al-15%B4C Composites Containing Sc and Zr

Abstract

Hot deformation behavior and processing maps of three Al-15%B4C composites denoted as the base composite (Al-15vol.%B4C), S40 (Al-15vol.%B4C-0.4wt.%Sc) and SZ40 (Al-15 vol.%B4C-0.4wt.%Sc-0.24wt.%Zr) were studied by uniaxial compression tests performed at various deformation temperatures and strain rates. The constitutive equations of the three composites were established to describe the effect of the temperature and strain rate on hot deformation behavior. Using the established constitutive equations, the predicted flow stresses on various deformation conditions agreed well with the experimental data. The peak flow stress of the composites increased with the addition of Sc and Zr, attributing to the synthetic effect of solute atoms and dynamic precipitation. The addition of Sc and Zr increased the activation energy for hot deformation of Al-B4C composites. The processing maps of the three composites were constructed to evaluate the hot workability of the composites. The safe domains with optimal deformation conditions were identified for all three composites. In the safe domains, dynamic recovery and dynamic recrystallization were involved as softening mechanisms. The addition of Sc and Zr limited the dynamic softening process, especially for dynamic recrystallization. The microstructure analysis revealed that the flow instability was attributed to the void formation, cracking and flow localization during hot deformation of the composites.